Both have advantages and disadvantages. Reverse flow will provide a more even temperature across the cooker. Really good when you want to cook a lot of meat at the same temp at the same time. On the other hand, once you get your cooker tuned with tuning plates, you are pretty much the same across the cooker temp wise BUT you can also move the plates around to cook at different temps.
Folks will swear both ways are the best. Depends on what you are used to and whether you are a Ford or Chevrolet guy.